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1.
We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.  相似文献   
2.
In the Calicut population of P. hydrodromous, eyestalk principles are either directly or indirectly involved in maintenance of the differential growth rate of the sexes during the latter half of the first year of the life cycle. The prebreeding season (September—November), which is distinct in crabs 4.0 cm and over in carapace width (cw), is either absent or not distinct in young females (cw 2.8–3.2 cm), though the latter enter their first reproductive cycle by December, when 8–9 mth old. December—March is a period of active vitellogenic growth; from March onwards, there is a distinct swing in favor of somatic growth in females, though the proecdysis per se is not initiated until May. A typical brachyuran, Paratelphusa restricts its reproductive activity to intermolt and somatic growth chiefly to premolt; there are, however, definite phases within the intermolt itself when the physiological tilt favors somatic growth or alternatively reproduction. In females above cw 4.0 cm, the tendency for somatic growth is suppressed once they attain this cw after the monsoon (June—July) molt; eyestalk ablation during the prebreeding season precipitates accelerated ovarian growth. Administration of β-ecdysone in premolt titers failed to restrain this ovarian response and to promote somatic growth sufficiently. Conceivably, gonadal growth-promoting principles keep under check the responsiveness of the target tissues involved in somatic growth perhaps by affecting ecdysone receptors. The present investigations do not indicate a vitellogenesis-inhibiting role for β-ecdysone.  相似文献   
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4.
Phylogenetic characters for Heteroderinae Luc. et al., 1988 are evaluated in Meloidodera which is believed to have primarily ancestral characters. Phasmid ultrastructure is observed in second-stage juveniles (J2), third-stage juvenile males, fourth-stage juvenile males, and fifth-stage males of Meloidodera floridensis and M. charis. Phasmid secretion occurs inside the egg before the J1-J2 molt. Before J2 hatch, concentric lamellar membranes occur within the sheath and socket cells. Some membranes become lamellae of the sheath cell plasma membrane; others become multilamellar bodies. During early molting, plasma membrane lamellae disappear and a distal dendrite segment appears in a rudimentary canal. After the molt, the distal dendrite is not present within the canal. The phylogenetic utility of phasmid features is discussed. In both species the ampulla shape and size between molts are stable features in juveniles and males. The posthatch J2 sheath cell receptor cavity may vary in a species specific manner, but comparative morphology requires precise timing after hatch.  相似文献   
5.
Calyx fluid and venom from the braconid parasitoid Microplitis demolitor differentially affected the development of Pseudoplusia includens and Heliothis virescens. P. includens exhibited delays in larval development, supernumerary instars, and formed larval-pupal intermediates when injected with 0.01-0.10 wasp equivalents of calyx fluid. In contrast, H. virescens was relatively unaffected by calyx fluid regardless of dose. Venom did not affect the development of either host species, but appeared to synergize the activity of calyx fluid. This was particularly evident in H. virescens, where injection of 0.10-0.20 wasp equivalents of calyx fluid and venom induced the formation of a large number of intermediates while the same amount of calyx fluid did not. The particulate portion of M. demolitor calyx fluid was the only component that caused developmental delays and the formation of intermediates in both host species. Purified virus caused developmental alterations in P. includens, while trioxsalen treated calyx fluid did not affect development of P. includens or H. virescens. These data suggest the requirement for venom in parasitism may differ between host species, and that dosage plays an important role in interpreting the interaction between calyx and venom components.  相似文献   
6.
【目的】了解黑胸散白蚁Reticulitermes chinensis Snyder末龄若虫的蜕皮羽化行为。【方法】室内恒温(26±0.5)℃恒湿(75%±5%)饲养黑胸散白蚁末龄若虫,间隔一定时间进行观察记录。【结果】黑胸散白蚁末龄若虫蜕皮羽化时间持续2~8 h。蜕皮一般从末龄若虫胸腹部交界处背部开始破裂,从腹末、翅末、足端、口器末端或触角端脱落,50%以上的正常羽化蜕皮是从腹末端脱落。初始羽化成虫为白色,随后身体和翅的颜色逐渐加深和变黑,羽化8~12 h后,虫体整体颜色变为黑色。室内观察结果还表明,34.7%的末龄若虫无法正常羽化。【结论】黑胸散白蚁末龄若虫蜕皮羽化持续时间较短,蜕皮一般是从胸腹部交界处背部开始破裂,但可从不同部位脱落,且蜕皮羽化行为容易受到外界环境的影响。  相似文献   
7.
The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus.  相似文献   
8.
本文用3种几丁质合成抑制剂卡死克、噻嗪酮和灭幼脲对意大利蝗Calliptatmnus italicus(L.)卵和3龄蝗蝻进行药剂试验.实验结果显示卡死克对意大利蝗药效最高:LC50、LC90分别为1.34、14.17 mg/L.灭幼脲次之LC50、LC90分别为2.09、45.22 mg/L.灭幼脲和卡死克在50 m...  相似文献   
9.
Gypsy moth, Lymantria dispar L., rate of larval development, molting, pupal weight and survival were studied on an artificial diet containing different concentrations of green ash ethyl acetate extractables (EtOAc Exts). Insects were reared on experimental diets from egg to pupa. Addition of EtOAc Exts to artificial diet significantly prolonged larval development and reduced their survival compared to larvae reared on control diet. Weights of pupae were significantly reduced when larvae were reared on diet containing the lowest dosage of EtOAc Exts (i.e., 0.01%) versus on control diet. EtOAc Exts in diet (e.g., 0.01, 0.06 and 0.2%) frequently caused incomplete ecdysis which invariably resulted in larval death. Impaired feeding, locomotion and excretion are likely causes of death. The combination of these results with our earlier findings of repellents and feeding deterrents against gypsy moth larvae (GML) in green ash foliage shows that the non-host status of green ash to the highly polyphagous GML involves three orders of chemical defense: repellents, feeding deterrents and inhibitors of nutritional and developmental physiology. As the insect becomes sequentially exposed to these orders of defense, it incurs higher costs because the adverse effects become less reversible.  相似文献   
10.
In chickens, high levels of dietary zinc cause molting, and the reproductive system undergoes complete remodeling concomitant to feather replacement. In the present study, the expression profiles of cytokines and chemokines were investigated in the ovary and oviduct of control hens and of hens induced to molt by zinc feeding. The zinc-induced feed-intake suppression, the changes in corticosterone levels, the immune cell populations in the reproductive tract, and the apoptosis of reproductive tissues were analyzed. The expression of mRNAs for interleukin-6 (IL-6), interferon-γ (IFN-γ), the avian ortholog of mammalian IL-8 (chCXCLi2), and a chicken MIP-1β-like chemokine (chCCLi2) in the ovary and of mRNAs for IL-1β, IL-6, IFN-γ, transforming growth factor-β2, chCXCLi2, and chCCLi2 in the oviduct were upregulated significantly during zinc-induced molting. A simultaneous feed-intake reduction was observed with higher expression of cytokines and chemokines. The results of the present investigation also suggested that the upregulation of corticosterone was closely associated with the increased expression of cytokines and chemokines. An increase in apoptosis within reproductive tissue during tissue regression was also noted. We had previously observed the upregulation of these cytokines expression in an earlier study (molting by feed withdrawal). However, the pattern and the level of expression were different among these two methods. These findings indicate that cytokines might be a common mediator of tissue regression during molting induced by diverse methods, although the pattern of induction is different. Thus, a high dose of dietary zinc seems to induce reproductive regression via the upregulation of cytokines and chemokines, the suppression of feed intake, and the increase in serum corticosterone, resulting finally in the apoptosis of reproductive tissues.  相似文献   
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